The eukaryotic-type membrane-associated serine-threonine sensor kinase (StkP) and PP2C phosphatase (PhpP) of Streptococcus pneumoniae regulate expression of genetic competence as well as virulence. In this study, we showed that PhpP activity is essential in a stkP+ genetic background, suggesting the tight control of StkP activity by PhpP. Results of co-immunoprecipitation analyses suggested that StkP and PhpP form a complex in the cell membrane fraction. Direct interaction between the N-terminal kinase domain of StkP and PhpP was also confirmed by using recombinant proteins. Flow cytometry analyses allowed the determination of the cytoplasmic localization of PhpP and the kinase domain of StkP on the membrane, whereas the StkP C-terminal penicillin-binding protein and serine-threonine-kinase-associated (PASTA) domain localized in the periplasm. These results provided the first genetic and physiological evidence that PhpP and StkP constitute a signaling couple.
(Research Team for Bacterial/Parasitic Diseases, TEL +81-29-838-7708)
Reference:
Osaki, M. et al. (2009) J. Bacteriol. 191:4943-4950.
